We have entered 20 patients with a variety of metastatic solid tumors on the twice weekly IV dose of 1 mg/meter squared and 4 mg/meter squared of the interferon inducer poly ICLC. We have not demonstrated an antitumor effect in any patient and have witnessed toxicity that included mild fevers, fatigue, nausea, and mild hypotension. Interferfon levels have been measured in all patients studied and are consistently higher in patients treated with 4 mg/meter squared. Immunologic monitoring has demonstrated a consistent enhancement of monocyte-mediated cytostasis, depression of mitogen-stimulated proliferative responses in vitro, and decreased or no change in natural killer activity.